Love enjoys knowing everything about you; desire needs mystery.

The one word I hear when people have affairs is that they feel alive. They don't talk about the fact they're having sex. They feel like they are engaged with their life. They describe an experience that beats back the deadness inside, which isn't the fault of the marriage or the partner. It's often the deadness that they have allowed to creep in for years on their own. But by definition, it's a transgressive act. And transgression is a breaking of the rules. And it gives you a sense of ownership and freedom. And ownership and freedom gives you a feeling of aliveness. It's a chain.

In dating, if you say no, your lover goes on to the next person. In marriage, if you say no, the person stays.

The attraction of dating is that you don't take yes for granted - - you're fully engaged, there's seductiveness, tension.

In committed sex, in marriage, people don't feel the need to seduce or to build anticipation - - that's an effort they think they no longer need to do now that they have conquered their partner. If they're in the mood, their partner should be too.

We know desire is rooted in absence and yearning. What you don't have is often ten times richer than what you actually experience. An affair is a perfect erotic plot because it fits the erotic equation of psychotherapist Jack Morin: "Attraction plus obstacle equals excitement.".

Affairs can be powerful detonators. They can invigorate a marriage that's flat, jolt people out of years of complacency. Fear of loss rekindles desire, makes people have conversations they haven't had in years, takes them out of their contrived illusion of safety.